Chinatown neighbors at the Chatham Square Redesign Task Force meeting on Monday did their best to point out flaws in the unpopular project — but time is running out.

A few hours before the meeting, the city Public Design Commission approved the redesign that the city says will improve auto traffic flow and pedestrian conditions and which will create new public open space.

But residents and merchants have been saying the $50 million project would not improve pedestrian safety, would reduce traffic lanes and create bottlenecks and would put new open space in the wrong place.

A four-year construction period during an economic recession that will coincide at some point with the two-year-long reconstruction of the Brooklyn Bridge and the simultaneous construction in Chatham Square on the city’s Third Water Tunnel is likely to wreak havoc on Chinatown businesses and the neighborhood’s quality of life, residents said at the Jan. 12 task force meeting.

However, Thomas Yu, a Community Board 3 member and chairperson of the task force, said the city intends to put the project out to bid this month and sign contracts for the work early in March.

“The city can do anything it wants,” Yu said. “We’re only advisory and we have a small window to try to work with the city. We can throw up our hands or try to see if we can help improve it.”

The task force, which includes C.B. 3 members, Chinatown residents and community leaders and public members, will be dismantled at the end of February, task force members said.

Brian Ketcham, the task force’s engineering consultant, told the meeting that he had asked the city about reopening Park Row, which has been closed to most traffic since the World Trade Center attack more than seven years ago in order to give smooth access to Police Headquarters.

“They said, ‘Not in your lifetime. There is no way you’ll see that happen,’” Ketcham reported.

The city’s plan assumes that Park Row will remain closed and realigns the intersection to connect E. Broadway to Worth St. and the Bowery to St. James Pl. The plan replaces half of Park Row’s largely unused roadbed with a promenade and park.

Ketcham questioned the adequacy of the city’s traffic survey of current conditions.

“They provided a report of the last five years of traffic accidents, and I’m surprised at how few accidents they report,” he said. Many people in Chinatown are skeptical of the survey, he noted.

Ketcham urged the task force to insist that the city conduct a pedestrian-vehicle-conflict survey.

“It’s very expensive,” he said. “You need a lot of people to make observations — like cars making people jump back from the curb.”

Ketcham said he has asked the city for more detailed traffic-simulation models with current traffic conditions for morning, midday and evening peak times in Chatham Square, as well as midday Saturdays, with diversions from Brooklyn Bridge.

“We haven’t yet seen the level of detail needed to estimate the impact of the Brooklyn Bridge reconstruction,” he said. The question is whether the Manhattan Bridge has the capacity to handle a doubling of traffic at certain times when Brooklyn Bridge traffic is diverted, he said. The issue also involves intersections like Flatbush Ave. and Tillary St. in Brooklyn, as well as the Bowery and Canal St. in Chinatown, Ketcham added.

He also noted that the city hasn’t estimated the diversion of westbound traffic onto Canal St.

The Brooklyn Bridge reconstruction is planned for about 12 weekends over the course of a 19-month period.

“They will be directing 4,000 more cars into your community from the second quarter of 2010 to the fourth quarter of 2011,” Ketcham warned.

Paul Lee, a former Chinatown merchant, said that weekend work on the Brooklyn Bridge was the worst schedule possible.

“The busiest day of the week for Chinatown is Sunday and the next busiest is Saturday,” he said.

The traffic impact of the large, new Marriage Bureau on Worth St. a few blocks west of Chatham Square was another concern.

The city claims most couples will come by public transport, Ketcham noted.

“I told [the city agencies] I’ve never seen anyone in a wedding gown on the subway,” he added.

Residents attending the meeting said the proposed public plaza on the west side of the Bowery at Chatham Square should be shaved by about 5 feet to provide another turning lane for southbound Bowery traffic onto westbound Worth St.

The problem is that Kimlau Arch would be in the way and would have to be moved 5 feet west. The arch, however, is located on designated New York State parkland and the state would have to give up the designation to accommodate the extra lane.

“Getting the state to give up parkland is a major undertaking,” Ketcham observed.

Shin-Pei Tsay, a deputy director of Transportation Alternatives — the pedestrian-and-cycling advocacy organization — dissented from most residents at the meeting and said that the design creates a simpler and more rational intersection at Chatham Square.

“Pedestrians have fewer crossovers, and crosswalks could be adjusted to provide the safest crossings,” she said.

The task force intends to meet three more times before it is disbanded. The next public meeting is Wed., Jan. 21, followed by Wed., Feb. 18. The last meeting is to be on Mon., Feb. 23.